1. Field
One feature generally relates to communication systems, and more particularly, to a method of providing multiple retransmission policies for different media access control protocol data units (MPDUs) within a single data stream.
2. Background
The increased availability of wireless local area networks (WLANs) has allowed stations, such as desktop computers, laptop computers, hand held personal digital assistants (PDAs), and mobile phones, to wirelessly connect with one another through a variety of networks, such as local area networks (LANs) and the Internet, to transfer data between them. For example, a user can take her laptop computer from her desk into a conference room to attend a meeting and still have access to her local network to retrieve data and have access to the Internet via one or more modems or gateways present on the local network without being tethered by a wired connection.
A WLAN may be comprised of four primary components. These components may include stations (STAs), access points (APs), a wireless medium and a distribution system. The network is built to transfer data between stations that may include computing devices with wireless network interfaces. For example, laptop computers, desktop computers, mobile phones, and other electronic devices having wireless network interfaces are examples of stations within a network. Access points are devices that allow stations to connect to one another and transfer data. Examples of access points include routers, centralized controllers, base stations, “node Bs,” or site controllers.
Data is transmitted over a WLAN via packets. Packets contain control information and payload information (e.g., the data); the form of packets vary depending on the communication protocol. A station may desire to transfer multimedia content, such as video, over the WLAN to another station via one or more access points. Typically, video traffic is mapped to a single priority level, which means that all frames in the video stream will have the same retransmission policy on a WLAN link between an access point and the destination station (station receiving the video data). However, some video frames may contain more important information than other video frames, and thus frames with less important information may be dropped with less consequence than frames with more important information.
For example, in some content distribution systems, hierarchical modulation schemes (also referred to as layered modulation schemes) may be implemented to deliver varying quality or resolution of video content. Such schemes often modulate multiple data streams/bitstreams into one single symbol stream or bitstream, comprising base layer bitstream/symbols and enhancement layer bitstream/symbols before transmission. Use of the enhancement layer permits improving video content quality and/or resolution at the receiving device(s). The first base layer bitstream may include a plurality of intra-coded picture frames (I-frames) and predicted picture frames (P-frames). The first enhancement layer bitstream includes a plurality of bi-predictive picture frames (B-frames). In such a scheme, data pertaining to I-frames and P-frames are more critical than data pertaining to B-frames. Other content distribution systems may also have properties such that certain frame data is more critical than other frame data.
Therefore, there is a need for a method to provide multiple retransmission policies for different data frames within a data stream, such as a video and/or audio data stream having a layered modulating scheme, that has a single priority level link between an access point and a station.